The role of intense magnetic fields in the enhancement of dose distributions of high energy electrons is being investigated. This project is based on the premise that an increase in the ratio of tumor dose to normal tissue dose will increase cure rates and decrease morbidity in cancer patients who receive radiation therapy. We are simulating the transport of high energy electrons in the presence of magnetic fields using Monte Carlo technique. It has been shown that a transverse magnetic field of 20-50 kilogauss enhances percent dose at a depth of 10 cm compared to the entrance dose by a factor of 1.5 to 2.0, and a longitudinal magnetic field significantly reduces the penumbra of the electron beams. Effects of different magnetic field profiles are being investigated in order to determine quantitatively the improvement in dose distributions by practical magnet systems. The effects of magnetic fields from magnets designed for clinical use on the dose distributions produced in an anthropomorphic phantom will be determined and an optimum design for a clinical magnet will be achieved.